Illuminating assembly for indicating instruments



ILLUMINATING ASSEMBLY FOR INDICATING INSTRUMENTS George K. C. Hardesty,Mayo, Md.

Original application August 22, 1952, Serial No. 305,930, now Patent No.2,738,759, dated March 20, 1956. Divided and this application December22,1955, Serial No. 554,900

3 Claims. (Cl. 116-1'29) (Granted under Title 35 U. S. Code (1952), sec.266) The invention described herein may be manufactured and used by orfor the Government of the United States of America for governmentalpurposes without the payment of any royalties thereon or therefor.

This application is a division of application, Serial No. 305,930, filedAugust 22, 1952, now United States Patent No. 2,738,759, granted March20, 1956, and relates to illumination of dial type instruments and, moreparticularly, to means providing for selective illumination of the full360 degrees of a dial, without shadow effects from electrical conductorsto the illuminating source, and more specifically to anelectroluminescent indicator therefor.

Various arrangements have previously been used for illuminating the faceof a clock, meter or other instrument to provide night visibilitythereof. Among these are edge illumination devices, which are generallycomplex and expensive with insufiicient illumination resulting from theineificient light transmission to the instrument face. Another form ofillumination involves a central light source within the face and infront of the dial, to which energy is supplied by conductors crossingthe dial face and thereby causing shadows and obscuring a portion of thedial and the indicia thereon, or interfering with the movement of anypointers associated therewith. Other dial illumination devices utilizean electric lamp in cooperation with a translucent pointer toselectively illuminate the indicia on the dial face. In all, theelectric lamp is subject to breakage and burnout.

The present invention is an improvement in selective face illuminationand is achieved by the employment of indicators or pointers havingelectro-luminescent light sources therein, said indicators cooperatingwith the dial face of the instrument which carries invisible conductorswhich supply energy to said light sources. The invisible conductors donot leave shadows or obscure indicia or indicator and do not interferewith movement of the indicators.

It is, therefore, an object of the invention to provide an illuminateddial and indicating means for an instrument which is lighted withoutobscurance of, or interference with, indications thereon and wherein theindicator provides the illumination therefor.

A further object of the invention is to provide simple and rugged meansof rendering a dial indication visible Which requires little or noservicing.

A still further object ofthe invention is to provide an indicatinginstrument having invisible means for energizing the indicating elementof the instrument.

Another object of the invention is to provide a dial indicatinginstrument having an electroluminescent indicator.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

The figure illustrates in partial vertical section the inventionemploying a single thickness of glass cover with a transparentconducting layer secured thereto and an electroluminescent indicatingmeans.

Referring now to the drawing, there is illustrated the upper portion ofan instrument 5 having a dial plate 6 with indicia 7 thereon, over whicha pointer indicator generally designated as 8, operates to provide theinformation desired. Shaft 9 shown broken away, extends to the mechanismof the instrument to provide rotation of the indicator 8.

The dial plate 6 is supported in any conventional manner in a casing 10,for instance, by rings 11 and 12 which may engage grooves or threads inthe casing 10 or may be secured thereto by soldering, screws, or thelike. The casing 10 is preferably provided with a rubber or plastic ring13 adapted to support a transparent instrument face consisting, forexample, of a laminated transparent structure including transparentplate 14 of glass or plastic, as may be desired, and having depositedthereon transparent conducting layer 15 employed for bringing electricalcurrent to the center of the instrument face for operating the indicatoror light source 8.

The conducting layer 15 is preferably provided at the edge of plate 14with a turned over portion 16, illustrated in the figure as turned overthe plate 14 to form a conductor around the periphery. While the layer15 is shown as having appreciable thickness it may consist of very thindeposited layers of material, such as might be applied by sputteringtechniques and may be of molecular dimensions. Where a thin depositedlayer of the conducting material is applied, it is preferable to employat least a large portion of the face area in order that the thinconductive layer may be able to carry sufiicient electrical currentwithout undue heating or voltage drop.

A power source 17 may be connected to the conducting layer 15 in anyconvenient manner as by pads, pressure plates, or other suitable contactmaking means. In the figure connection is made by means of a ring 18within the casing and extending circumferentially around plate 14. Ring18 is adapted to fit snugly against the turned up portion 16 and isillustrated as forming electrical contact between the portion 16 and alead 19 passing through the casing 10. Ring 18 is insulated from thecasing 10 by a rubber or plastic ring 20. The illuminable indicatormember 8 is illustrated as attached to shaft 9, the member 8 being ofspecial design to render the same visible apart from generalillumination of the face. The plate 14 and conducting layer 15 thereoncooperate with a pad or contacting member 21 centrally located forsupplying energy to the illuminable member 8 and the other terminalshown as a ground connection 22 connected to shaft. This embodimentpermits the use of the position indicating member 8 without generalillumination. The indicating member comprises a metallic backing at 23with a coating of material 24 thereon which is electro-luminescent. Thismaterial has the characteristic of visibly glowing when an electricpotential is imposed thereacross. For this purpose, a layer oftransparent conducting material 25 may be deposited on the layer 24 ofluminescent material. A flexible lead, or pig tail, 26, soldered orotherwise attached at 27 extends from the layer 25 to make contact withthe pad 21 and circuit of layer 15, which serves to distributeelectrical potential over the front face of the indicator element. Thelayer 24 is non-conducting and supports the potential difference appliedbetween layer 25 and member 23, the latter member being grounded throughshaft 9. In this case only the illuminated indicating member or pointer8 is seen as the instrument 5 is observed.

It may be noted that when the resistance of the thin sheet conductor orlayer 15 is selected to provide particu Patented May 21 1957" masses latvoltage drops and consequent heating effects as desired the transparentface conductor becomes an eflicient means for defrosting and forpreventing formation of moisture on, or fogging of, the instrument face.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood, that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. An illuminated indicator comprising a casing having a dial platesecured therein, indicia means mounted upon said dial plate, shaft meansmounted within said casing, a composite transparent conducting faceplate comprising transparent conducting means, electric potentialdistributing means concentrically connected to said transparentconducting means, an indicating member secured to said shaft means, andcomprising a rnetalic backing having an electro-luminescent means and atransparent conducting means mounted thereon, connecting means couplingsaid transparent conducting means and said electric potentialdistributing means to thereby energize said indicating member to avisible glow.

2. An illuminating instrument comprising a dial and indicating meansassociated therewith including a transparent cover plate having thereona transparent electric conducting surface, a movable indicator providingan indication and having means illuminating said indicator whenelectrically energized, means supporting said indicator, and circuitmeans including said conducting surface and said supporting means forenergizing said indicator illuminating means.

3. An illuminated instrument comprising a casing having a stationarydial plate secured therein, indicia means mounted on said dial plate,rotatable shaft means mounted within the casing centrally of the dialplate, a composite transparent conducting face plate mounted in front ofthe stationary dial and comprising transparent conducting means,electric potential distributing means concentrically connected to thetransparent conducting means, a pointer secured to said shaft means,said pointer comprising a metalic backing member grounded to the shaftand having an electro-luminescent means and a transparent conductingmeans superimposed thereon, and connecting means coupling the electricpotential distributing means to the transparent conducting means of thepointer to thereby energize the pointer to a visible glow.

Electrical Construction and Maintenance, February 1952 issue.

